Armature Voltage Calculator for DC Motor
Easily calculate armature voltage for DC motors using speed, torque, current, and resistance. Includes formulas, examples, and a step-by-step guide.
torque and armature voltage relation
The armature (terminal) voltage of a DC motor can be computed by: V a = E b + I a R a. Calculate back-EMF Eb at speed: E b = k e o, being able to find its speed (omega) = rad/s or E b = (k e n) at speed = rpm, depending on your constant. Assuming that torque and motor constant are known, obtain I a = T / k t and then V a = E b + (T/k t) R a.
Formula & Table Summary:
- Armature (terminal) voltage: Va = Eb + Ia·Ra
- Back EMF (constant flux): Eb = ke · ω (V, ω in rad/s) or Eb = ke_r · n (n in rpm)
- Torque ↔ Current (constant flux): T = kt · Ia → Ia = T / kt
- Speed conversion: ω (rad/s) = 2π·n / 60
Converter: Input → Output
| Input available | Use / Formula | Output |
|---|---|---|
| Speed (n rpm), motor constant ke_r, Ia, Ra | Eb=ke_r·n → Va=Eb+Ia·Ra | Armature voltage Va (V) |
| Torque T, kt, speed (n) and Ra | Ia=T/kt; Eb=ke_r·n; Va=Eb+Ia·Ra | Va (V) |
| Measured Va, Ia, Ra | Eb=Va−Ia·Ra; speed from Eb/ke | Back EMF Eb and speed |
dc motor resistance calculator
Armature voltage to a DC motor is the terminal voltage Which is applied between the armature winding that develops the needed armature current and back EMF. In the case of a simple DC motor: V a = E b + I a R a, V a is armature (terminal) voltage, E b is back EMF (inversely proportional to speed and flux), I a is armature current and R a is armature resistance. Back EMF may be given as Eb = ke x Ph w (or Eb = ke x w ) and torque as T = kt x Ph x Ia (or T = kt x Ia x). This manual provides the basic equations, a table of input/output converters, and some sample calculations to calculate armature voltage using speed, torque, current, resistance, or motor constants.
dc motor efficiency calculator
| Scenario | Input | Calculation | Result |
|---|---|---|---|
| Given speed & current | n = 1500 rpm, ke_r=0.04 V/rpm, Ia=10 A, Ra=0.5 Ω | Eb=0.04×1500=60 V; Va=60+10×0.5 | Va=65.0 V |
| Given torque & speed | T=20 N·m, kt=0.5 N·m/A, n=1000 rpm, ke_r=0.05 V/rpm, Ra=0.2 Ω | Ia=20/0.5=40 A; Eb=0.05×1000=50 V; Va=50+40×0.2 | Va=58.0 V |
| Back-calc speed | Measured Va=220 V, Ia=5 A, Ra=1 Ω, ke_r=0.1 V/rpm | Eb=220−5×1=215 V; n=Eb/ke_r | n=215 / 0.1 = 2150 rpm |
| Low-current small motor | n=3000 rpm, ke_r=0.02 V/rpm, Ia=0.5 A, Ra=2 Ω | Eb=0.02×3000=60 V; Va=60+0.5×2 | Va=61.0 V |
